Self-limiting atomic thermal etching systems and methods

ABSTRACT

Systems and methods of etching a semiconductor substrate may include flowing an oxygen-containing precursor into a substrate processing region of a semiconductor processing chamber. The substrate processing region may house the semiconductor substrate, and the semiconductor substrate may include an exposed metal-containing material. The methods may include flowing a nitrogen-containing precursor into the substrate processing region. The methods may further include removing an amount of the metal-containing material.

TECHNICAL FIELD

The present technology relates to semiconductor systems, processes, and equipment. More specifically, the present technology relates to systems and methods for selectively etching metal-containing materials utilizing an atomic layer etching process.

BACKGROUND

Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers, or thinning lateral dimensions of features already present on the surface. Often it is desirable to have an etch process that etches one material faster than another facilitating, for example, a pattern transfer process. Such an etch process is said to be selective to the first material. As a result of the diversity of materials, circuits, and processes, etch processes have been developed with a selectivity towards a variety of materials.

Etch processes may be termed wet or dry based on the materials used in the process. A wet HF etch preferentially removes silicon oxide over other dielectrics and materials. However, wet processes may have difficulty penetrating some constrained trenches and also may sometimes deform the remaining material. Dry etches produced in local plasmas formed within the substrate processing region can penetrate more constrained trenches and exhibit less deformation of delicate remaining structures. However, local plasmas may damage the substrate through the production of electric arcs as they discharge. Additionally, plasma effluents can damage chamber components that may require replacement or treatment.

Thus, there is a need for improved systems and methods that can be used to produce high quality devices and structures. These and other needs are addressed by the present technology.

SUMMARY

The present technology includes systems and methods of etching a semiconductor substrate. Exemplary methods may include flowing an oxygen-containing precursor into a substrate processing region of a semiconductor processing chamber. The substrate processing region may house the semiconductor substrate, and the semiconductor substrate may include an exposed metal-containing material. The methods may include flowing a nitrogen-containing precursor into the substrate processing region. The methods may further include removing an amount of the metal-containing material.

In some embodiments the oxygen-containing precursor may be configured to react with the metal-containing material to produce a modified metal-containing material. The nitrogen-containing precursor may be configured to react with the modified metal-containing material to produce a volatile complex. The oxygen-containing precursor may include water or radical oxygen, and the nitrogen-containing precursor may include an amine. For example, the amine may include diethylamine, propylamine, or N-ethylmethylamine in embodiments.

In some embodiments, the oxygen-containing precursor and the nitrogen-containing precursor may be flowed sequentially into the substrate processing region. The methods may also include holding for a first period of time subsequent flowing the oxygen-containing precursor and prior to flowing the nitrogen-containing precursor. In some embodiments, the first period of time may be between about 5 seconds and about 30 seconds. The methods may also include holding for a second period of time subsequent flowing the nitrogen-containing precursor. In some embodiments, the second period of time may be between about 10 seconds and about 60 seconds. The oxygen-containing precursor and the nitrogen-containing precursor may be halogen free, and in embodiments all precursors utilized may be halogen free. The method may also include a plasma-free process in some embodiments. Exemplary methods may be performed at a temperature of between about 100° C. and about 225° C. In some embodiments, flowing the oxygen-containing precursor and flowing the nitrogen-containing precursor may be repeated in at least one additional cycle. In some embodiments, the metal-containing material may include titanium nitride.

The present technology also includes methods of etching a semiconductor substrate. The methods may include forming plasma effluents of an oxygen-containing precursor in a remote plasma region of a semiconductor processing chamber. The methods may include flowing the plasma effluents into a substrate processing region housing the semiconductor substrate. In some embodiments the semiconductor substrate may include an exposed metal-containing material. The substrate processing region may be fluidly coupled with the remote plasma region. The methods may include holding for a first period of time greater than or about 1 second. The methods may also include flowing a nitrogen-containing precursor into the substrate processing region. The methods may further include holding for a second period of time greater than or about 1 second. The methods may also include removing an amount of the metal-containing material.

In some embodiments, the methods may further include flowing additional nitrogen-containing precursor into the substrate processing region. Exemplary methods may remove at least about 0.2 Å per cycle of flowing the plasma effluents and flowing the nitrogen-containing precursor into the substrate processing region. In some embodiments the nitrogen-containing precursor may be selected from the group of precursors consisting of a water-methylamine solution, a water-ethylamine solution, diethylamine, propylamine, dipropylamine, a water-diethylamine solution, and N-ethylmethylamine. In some embodiments the plasma effluents may be produced at a plasma power below or about 500 W.

Such technology may provide numerous benefits over conventional systems and techniques. For example, selectively removing particular metal-containing materials may allow other exposed structures to be maintained, which may improve device integrity. Additionally, the materials utilized may allow the selective removal of materials that previously could not be readily removed. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings.

FIG. 1 shows a top plan view of an exemplary processing system according to the present technology.

FIG. 2 shows a schematic cross-sectional view of an exemplary processing chamber according to the present technology.

FIG. 3 shows selected operations in a method of selectively etching a semiconductor substrate according to the present technology.

FIGS. 4A-4B illustrate cross-sectional views of substrate materials on which selected operations are being performed according to embodiments of the present technology.

FIG. 5 shows a chart illustrating etch amounts for various materials according to embodiments of the present technology.

Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes, and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations, and may include additional or exaggerated material for illustrative purposes.

In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter.

DETAILED DESCRIPTION

The present technology relates to removal of material layers from semiconductor substrates. During processing, such as back-end-of-line processing, materials may be removed to expose underlying structures. The underlying structures may include a number of materials formed throughout the manufacturing process, which may be exposed during material removal. For example, hard mask materials such as titanium nitride may be removed to expose underlying features, which may include exposed copper, carbon-containing materials, oxide-containing materials, nitride-containing materials, low-k dielectrics, and other materials. Removal of the hard mask material may expose the underlying materials to etchants that may also react with the underlying materials. As feature sizes continue to reduce and aspect ratios continue to increase, wet etchants that may be tailored to particular materials for removal may no longer be viable. The surface tension of the etchants applied to the substrates may deform or collapse the delicate features, which may cause device failure.

Dry etchant processes have been developed to attempt to remove certain materials. These processes may include atomic layer etching, which may be similar to atomic layer deposition in some ways, such as the sequential application of precursors to remove thin layers of material at a time. Conventional atomic layer etching may utilize a first precursor to modify a surface material, and a second material to sputter or etch the modified material. These conventional processes, however, may not be suitable for all materials, and may damage underlying structures. For example, as feature sizes are reduced, the amount of any particular material may become too thin or narrow to allow removal during operations intended to remove alternative materials. Especially for back-end-of-line operations, many different materials may be exposed at a single time, which when contacted by etchants may be removed in addition to the intended materials. Many conventional processes utilize halogen-containing etchants, which may etch many of the exposed materials in addition to the intended layers, or may etch other exposed materials faster than the intended targets. Additionally, plasma-based operations may sputter and damage exposed surfaces or underlying materials at effective plasma powers.

The present technology overcomes these deficiencies by utilizing a cyclic atomic layer etching process that may selectively remove certain materials over other exposed materials on a substrate. For example, the present technology may selectively remove titanium nitride and tantalum nitride over other exposed materials to allow the selective removal of hard mask and other material layers. Some embodiments produce these results by utilizing a halogen-free and plasma-free process that may selectively remove certain materials while substantially or essentially maintaining other material layers. Additionally, some embodiments may produce these results by utilizing a lower plasma power to produce etchant precursors than previously employed. By utilizing the disclosed atomic layer etching processes, a self-limiting removal may be performed to allow thin layers of material, such as monolayers, to be removed during individual cycles.

Although the remaining disclosure will routinely identify specific semiconductor structures, the present technology may not be so limited to back-end-of-line hard mask removal. For example, the selective removal techniques discussed throughout the present technology may be performed with a variety of high-aspect-ratio features of semiconductor devices that may include one or more of the materials discussed. The techniques may obviate additional etching and removal operations, and may obviate over-deposition of materials that may be removed but are to be maintained to a certain thickness after other material removal. Accordingly, the present technology encompasses selective etching as may be applied in any number of semiconductor and industry processes beyond those discussed herein. After identifying one exemplary system in which the present structures may be formed, the disclosure will discuss specific structures, as well as methods of performing selective removal of individual materials utilizing an atomic layer etching technique.

FIG. 1 shows a top plan view of one embodiment of a processing system 100 of deposition, etching, baking, and curing chambers according to disclosed embodiments. In the figure, a pair of front opening unified pods (FOUPs) 102 supply substrates of a variety of sizes that are received by robotic arms 104 and placed into a low pressure holding area 106 before being placed into one of the substrate processing chambers 108 a-f, positioned in tandem sections 109 a-c. A second robotic arm 110 may be used to transport the substrate wafers from the holding area 106 to the substrate processing chambers 108 a-f and back. Each substrate processing chamber 108 a-f, can be outfitted to perform a number of substrate processing operations including the etch processes described herein in addition to cyclical layer deposition

(CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, orientation, and other substrate processes.

The substrate processing chambers 108 a-f may include one or more system components for depositing, annealing, curing and/or etching material films on the substrate wafer. In one configuration, two pairs of the processing chamber, e.g., 108 c-d and 108 e-f, may be used to deposit dielectric material on the substrate, and the third pair of processing chambers, e.g., 108 a-b, may be used to etch the deposited dielectric. In another configuration, all three pairs of chambers, e.g., 108 a-f, may be configured to etch a material on the substrate. Any one or more of the processes described below may be carried out in chamber(s) separated from the fabrication system shown in different embodiments. It will be appreciated that additional configurations of deposition, etching, annealing, and curing chambers for dielectric films are contemplated by system 100. Many chambers may be utilized in the processing system 100, and may be included as tandem chambers, which may include two similar chambers sharing precursor, environmental, or control features.

FIG. 2 shows a cross-sectional schematic of an exemplary processing chamber 200 that may be utilized in operations of the present technology. Chamber 200 may be used, for example, in one or more of the processing chamber sections 108 of the system 100 previously discussed. Chamber 200 may deliver and activate precursors via thermal heating, or may utilize plasma generation. A remote plasma system (“RPS”) 210 may process a gas which then travels through a gas inlet assembly 211. Two distinct gas supply channels may be present within the gas inlet assembly 211. A first channel 212 may carry a gas that passes through the RPS 210, while a second channel 213 may bypass the RPS 210. The first channel 212 may be used for the process gas and the second channel 213 may be used for a treatment gas in disclosed embodiments. The lid or conductive top portion 221 and a perforated partition, such as showerhead 253, are shown with an insulating ring 224 disposed between, which may allow an AC potential to be applied to the lid 221 relative to showerhead 253. The process gas may travel through first channel 212 into chamber plasma region 220 and may be excited by a plasma in chamber plasma region 220 alone or in combination with RPS 210. The combination of chamber plasma region 220 and/or RPS 210 may be referred to as a remote plasma system herein. The perforated partition or showerhead 253 may separate chamber plasma region 220 from a substrate processing region 270 beneath showerhead 253. Showerhead 253 may allow a plasma present in chamber plasma region 220 to avoid directly exciting gases in substrate processing region 270, while still allowing excited species to travel from chamber plasma region 220 into substrate processing region 270.

Showerhead 253 may be positioned between chamber plasma region 220 and substrate processing region 270 and allow plasma effluents or excited derivatives of precursors or other gases created within chamber plasma region 220 to pass through a plurality of through-holes 256 that traverse the thickness of the plate or plates included in the showerhead. The precursors and/or plasma derivatives may combine in processing region 270 in order to produce films that may be deposited on substrate 280 positioned on a substrate support 275. The showerhead 253 may also have one or more hollow volumes 251 that can be filled with a precursor in the form of a vapor or gas, and pass through small holes 255 into substrate processing region 270, but not directly into chamber plasma region 220. Showerhead 253 may be thicker than the length of the smallest diameter 250 of the through-holes 256 in disclosed embodiments. In order to maintain a significant concentration of excited species penetrating from chamber plasma region 220 to substrate processing region 270, the length 226 of the smallest diameter 250 of the through-holes may be restricted by forming larger diameter portions of through-holes 256 part way through the showerhead 253. The length of the smallest diameter 250 of the through-holes 256 may be the same order of magnitude as the smallest diameter of the through-holes 256 or less in disclosed embodiments.

In the embodiment shown, showerhead 253 may distribute, via through-holes 256, process gases which contain a plasma vapor/gas as well as unexcited precursors. Additionally, the showerhead 253 may distribute, via smaller holes 255, additional precursors that are maintained separately from the plasma region 220. The process gas or gases may be maintained fluidly separate via the showerhead 253 until the precursors separately enter the processing region 270. The precursors may contact one another once they enter the processing region and react or may be provided sequentially and purged in between the deliveries to perform atomic layer processing.

Chamber 200 may be used to deposit or etch materials or perform operations discussed in relation to the present technology. Chamber 200 may also be utilized without plasma formation in the operations performed, and may instead thermally activate precursors delivered into the chamber, or may allow precursors to chemically react with one another. Chamber 200 is included only as an exemplary chamber that may be utilized in conjunction with the present technology. It is to be understood that operations of the present technology may be performed in chamber 200 or any number of other deposition, etching, or reactive chambers.

Turning to FIG. 3 is shown selected operations in a method 300 of selectively etching a metal-containing material, one or more of which may be performed, for example, in the chamber 200 as previously described, or in different chambers. Method 300 may include one or more operations prior to the initiation of the method, including front-end processing, deposition, etching, polishing, cleaning, or any other operations that may be performed prior to the described operations. A processed substrate, which may be a semiconductor wafer of any size, may be positioned within a chamber for the method 300. In embodiments the operations of method 300 may be performed in multiple chambers depending on the operations being performed.

Additionally, in embodiments the entire method 300 may be performed in a single chamber to reduce queue times, contamination issues, and vacuum break. Subsequent operations to those discussed with respect to method 300 may also be performed in the same chamber or in different chambers as would be readily appreciated by the skilled artisan.

Method 300 may include flowing an oxygen-containing precursor into a substrate processing region of a semiconductor processing chamber at operation 305. The semiconductor substrate may include one or more exposed regions of metal-containing material, and may include at least one other exposed material in embodiments, although multiple materials may be exposed on a substrate including the metal-containing material. Method 300 may optionally include performing a process hold at operation 310, which may allow time for the oxygen-containing precursor to interact or react with the metal-containing material. The hold may be performed for a first period of time.

The method may additionally include flowing a nitrogen-containing precursor into the substrate processing region at operation 315. The nitrogen-containing precursor may be flowed subsequent to the flow of the oxygen-containing precursor, such as in a sequential manner, and the nitrogen-containing precursor may be flowed subsequent the first period of time of the process hold. A second process hold may optionally be performed at operation 320 subsequent flowing the nitrogen-containing precursor. The second process hold may be performed for a second period of time to allow the nitrogen-containing precursor to react or interact with the metal-containing material. In some embodiments certain operations may be repeated in a number of cycles. For example, one or more of operations 305, 310, 315, or 320 may be repeated a number of times. At operation 325, an amount of the metal-containing material may be removed from the semiconductor substrate. Additional operations may also be included such as purging excess precursor with an inert precursor or pumping excess precursor or removed metal-containing material from the processing region or chamber.

As previously discussed, the present technology may perform an atomic layer removal of material from a semiconductor substrate. The first precursor flowed may interact with a surface layer of the metal-containing material to produce a modified metal-containing material. In one non-limiting example, the oxygen-containing precursor may react with a hard mask material, such as titanium nitride, to oxidize an amount of the metal-containing material. This modification may occur only at a surface level of the metal-containing material, or may occur to a controlled depth within the metal-containing material. For example, the metal-containing material may be modified, such as oxidized, to a first depth within the metal-containing material. In some embodiments, the metal-containing material may be modified greater than, about, or less than 10 nm. In some embodiments, the metal-containing material may be modified less than or about 9 nm, less than or about 8 nm, less than or about 7 nm, less than or about 6 nm, less than or about 5 nm, less than or about 4 nm, less than or about 3 nm, less than or about 2 nm, less than or about 1 nm, less than or about 9 Å, less than or about 8 Å, less than or about 7 Å, less than or about 6 Å, less than or about 5 Å, less than or about 4 Å, less than or about 3 Å, less than or about 2 Å, less than or about 1 Å, less than or about 0.9 Å, less than or about 0.8 Å, less than or about 0.7 Å, less than or about 0.6 Å, less than or about 0.5 Å, less than or about 0.4 Å, less than or about 0.3 Å, less than or about 0.2 Å, less than or about 0.1 Å, or less, and may be modified at only a single layer or monolayer of the structure. For example, only a top monolayer of the metal-containing material may be modified in embodiments.

The oxygen-containing material may be purged from the processing region in some embodiments prior to the introduction of the nitrogen-containing precursor. The purge may occur by a pumping system of the chamber that removes unreacted precursors from the substrate processing region, for example. Also, the oxygen-containing precursor may be pulsed into the chamber to limit the amount of oxygen-containing precursor utilized, or to limit or control the amount of interaction between the oxygen-containing precursor and the metal-containing material. The nitrogen-containing precursor may be subsequently flowed into the substrate processing region to interact with the modified metal-containing material in embodiments. The nitrogen-containing precursor may react with modified portions of the metal-containing material, while having limited or no interaction with unmodified portions of the metal-containing material.

The nitrogen-containing precursor may produce a complex of the modified metal-containing material, and in embodiments, this complex may be volatile. The volatile material may desorb from the surface of the metal-containing material, which may produce the material removal discussed above. The amount of removal may be determined by the amount of modified material produced by the first precursor, such as an oxygen-containing precursor. The second precursor, such as the nitrogen-containing precursor, may preferentially or exclusively react with modified material to produce a volatile complex that may be removed. In this way, method 300 may provide a self-limiting removal, where modified material may be removed from the surface of the substrate, or from the surface of the metal-containing material, while unmodified material remains. Once the modified material has been removed from the surface, no further reaction may occur from the nitrogen-containing precursor.

The oxygen-containing precursor may be or include any material including oxygen. These materials may include oxygen, water, ozone, nitrogen-and-oxygen-containing precursors, and other materials that may include oxygen in the chemical structure. The oxygen-containing precursor may be flowed through a plasma prior to delivery to the substrate, and in alternative embodiments the oxygen-containing precursor may not be flowed through a plasma prior to delivery to the substrate. For example, a plasma may be formed from an oxygen-containing precursor, such as oxygen, and the plasma effluents may be flowed to the substrate for interaction with the metal-containing materials. In other embodiments an oxygen-containing precursor, such as water or water vapor, may be flowed directly to the substrate to interact with the metal-containing material.

The nitrogen-containing precursor may be any nitrogen-containing material, and in some embodiments, the nitrogen-containing precursor may be or include an amine. The amine may react with an oxidized metal-containing material to produce a complex, which may be a volatile complex. Based on process conditions discussed below, the volatile complex may desorb from the surface of the metal-containing material and be removed from the chamber. Exemplary amines may include one or more amines alone, or may include one or more solutions of aqueous amines. For example, amines suitable for the present technology may include primary amines, secondary amines, tertiary amines, or cyclic amines. Exemplary amines may include one or more alkyl moieties, aryl moieties, aromatic moieties, or some other combination. Although any amine may be used in the present technology, exemplary amines may include ammonia, methylamine, diethylamine, propylamine, dipropylamine, N-ethylmethylamine, or other amines, anilines, and nitrogen-containing materials. Anilines may include any halogenated anilines, which may include, for example, 2-fluoroaniline, 2-fluoro-6-(trifluoromethyl)aniline, 2-fluoro-3-(trifluoromethyl)aniline. Additional precursors may include silicon-containing precursors, including halogenated silicon-containing precursors. For example, in embodiments trimethyl(trifluoromehtyl) silane may be used.

Aqueous solutions of amines may also be used in exemplary embodiments, and may include a water solution of methylamine, ethylamine, diethylamine, or any other amine or nitrogen-containing material. The amount of water in the solution may be between about 10% and about 90% in embodiments, and may be between about 30% and about 60% in embodiments. Solutions including both water and an amine may adjust the method 300 to include a single operation of flowing the amine solution into the processing region to etch a portion of the metal-containing material.

The oxygen-containing precursor and the nitrogen-containing precursor may be flowed sequentially into the substrate processing region, and the flow of each material may be a pulsed delivery into the processing chamber. The time of each pulse may be similar or different between the oxygen-containing precursor and the nitrogen-containing precursor, and may be similar or different between cycles of the method as well. The pulse time for any of the precursors may be less than or about 30 seconds in embodiments, and may be less than or about 20 seconds, less than or about 10 seconds, less than or about 8 seconds, less than or about 6 seconds, less than or about 4 seconds, less than or about 2 seconds, less than or about 1 seconds, less than or about 0.9 seconds, less than or about 0.8 seconds, less than or about 0.7 seconds, less than or about 0.6 seconds, less than or about 0.5 seconds, less than or about 0.4 seconds, less than or about 0.3 seconds, less than or about 0.2 seconds, less than or about 0.1 seconds, or less in embodiments. Because some embodiments may seek to remove only a monolayer or a few monolayers of material with each cycle, the pulse time may be between about 0.1 seconds and about 5 seconds in embodiments, or may be between about 0.1 seconds and about 2 seconds, or between about 0.1 seconds and 1 second in embodiments.

The amount of time during which the hold operations are performed may also affect etch rate and amount. For example, the longer the hold time, the more metal-containing material may be modified. Accordingly, in embodiments, the hold time may be greater than or about 1 second in embodiments, and may be greater than or about 5 seconds, greater than or about 10 seconds, greater than or about 15 seconds, greater than or about 20 seconds, greater than or about 25 seconds, greater than or about 30 seconds, greater than or about 35 seconds, greater than or about 40 seconds, greater than or about 45 seconds, greater than or about 50 seconds, greater than or about 55 seconds, greater than or about 60 seconds, or longer. The hold time may be affected by the amount of precursor utilized in embodiments. For example, a plateau may occur in the amount of material modified or removed during either of the hold times, which may indicate the end of either of the half-reactions or removal in the method. The time held for each operation may be adjusted up or down based on the occurrence of such a plateau to limit the effect on queue times for the method.

Process conditions may affect one or more aspects of the methods of the present technology. Temperature may be adjusted to cause, increase the efficiency of, or otherwise contribute to the operations of the method. One or more operations of method 300 may be performed at a temperature greater than or about 80° C. In some embodiments, the temperature may be greater than or about 90° C., greater than or about 100° C., greater than or about 110° C., greater than or about 120° C., greater than or about 130° C., greater than or about 140° C., greater than or about 150° C., greater than or about 160° C., greater than or about 170° C., greater than or about 180° C., greater than or about 190° C., greater than or about 200° C., greater than or about 210° C., greater than or about 220° C., greater than or about 230° C., greater than or about 240° C., greater than or about 250° C., greater than or about 260° C., greater than or about 270° C., greater than or about 280° C., greater than or about 290° C., greater than or about 300° C., greater than or about 310° C., greater than or about 320° C., greater than or about 330° C., greater than or about 340° C., greater than or about 350° C., or higher. In embodiments the temperature may be any temperature included within one of these ranges, or a smaller range encompassed by any of these ranges or noted temperatures.

By maintaining the temperature above or about 100° C. in embodiments, additional energy sources to initiate one or more of the reactions may not be needed. Additionally, temperatures above about 100° C. may allow the complex formed between the modified or oxidized metal-containing material to desorb from the surface of the metal-containing material. Upon contact of the nitrogen-containing precursor to the modified or oxidized metal-containing material, the volatile complex may be formed and desorbed simultaneously, and then may be removed from the processing region or chamber.

Additional chamber conditions including pressure may be adjusted to affect the operations being performed, such as the etch rate of the metal-containing material. The pressure within the chamber may be maintained between about 50 mTorr and about 10 Torr in embodiments. The pressure may also be maintained below or about 5 Torr, below or about 3 Torr, below or about 2 Torr, below or about 1 Torr, below or about 900 mTorr, below or about 800 mTorr, below or about 700 mTorr, below or about 600 mTorr, below or about 500 mTorr, below or about 400 mTorr, below or about 300 mTorr, below or about 200 mTorr, below or about 100 mTorr, below or about 90 mTorr, below or about 80 mTorr, below or about 70 mTorr, below or about 60 mTorr, below or about 50 mTorr, or less. Additionally, in some embodiments the pressure may be maintained between about 100 mTorr and about 1 Torr, and may be maintained between about 100 mTorr and about 800 mTorr, between about 100 mTorr and about 600 mTorr, or between about 200 mTorr and about 400 mTorr.

The pressure may be adjusted based on the pulse time of any of the precursors. For example, increasing the pulse time of a precursor may increase the pressure within the chamber. The pressure may be reduced subsequent a pulse of material, by pumping down the chamber, or may be maintained at an increased pressure. For example, by increasing the pulse time of water vapor, the overall etch time may not be affected. However, increasing the pulse time and the pressure within the processing region may increase the thickness of the oxide layer formed on the metal-containing material. For example, by increasing the oxygen-containing precursor pulse time from about 0.5 seconds to about 2 seconds and allowing the pressure to increase from about 400 mTorr to about 800 mTorr may increase the oxide thickness by over 2 nm, and may increase the thickness by over 3 nm or more.

The amount of nitrogen-containing precursor may affect the etch rate of the process and may depend on the oxide thickness formed on the metal-containing material. For example, a pulse of nitrogen-containing precursor may only remove a certain amount of modified metal-containing material. However, by flowing additional nitrogen-containing precursor into the processing region, a further amount of modified metal-containing material may be removed if there is residual modified material that was not fully removed with the first pulse of nitrogen-containing precursor. Accordingly, process queue times may be reduced by modifying the metal-containing material to a greater depth, and then performing multiple cycles of the nitrogen-containing precursor delivery to sequentially etch and remove layers of the modified metal-containing material. Thus, for every one operation of flowing the oxygen-containing precursor into the processing chamber and performing a hold for a first period of time, multiple operations of flowing the nitrogen-containing precursor may be performed.

Each operation of flowing the nitrogen-containing precursor may include performing a hold as discussed above, such that both flowing the nitrogen-containing precursor and performing a hold for a second period of time may be performed. In some embodiments, for each operation of flowing the oxygen-containing precursor into the processing region, the operation of flowing the nitrogen-containing precursor may be repeated one or more times, and may be repeated at least 2 times, at least 3 times, at least 4 times, at least 5 times, at least 6 times, at least 7 times, at least 8 times, at least 9 times, at least 10 times, at least 11 times, at least 12 times, at least 13 times, at least 14 times, at least 15 times, or more depending on the depth of the modification, such as oxidation to the metal-containing material.

The total number of cycles of any operation of method 300, including either or both of flowing the oxygen-containing precursor and flowing the nitrogen-containing precursor, along with any accompanying hold period, may be based on a desired depth of etching of the metal-containing material. For example, each cycle of method 300 may etch a certain amount of metal-containing material, and may etch at least about 0.05 Å per cycle. In some embodiments, method 300 may etch at least about 0.08 Å per cycle, and may etch at least about 0.1 Å per cycle, at least about 0.12 Å per cycle, at least about 0.14 Å per cycle, at least about 0.16 Å per cycle, at least about 0.18 Å per cycle, at least about 0.2 Å per cycle, at least about 0.22 Å per cycle, at least about 0.24 Å per cycle, at least about 0.26 Å per cycle, at least about 0.28 Å per cycle, at least about 0.3 Å per cycle, at least about 0.32 Å per cycle, at least about 0.34 Å per cycle, at least about 0.36 Å per cycle, at least about 0.38 Å per cycle, at least about 0.4 Å per cycle, at least about 0.42 Å per cycle, at least about 0.44 Å per cycle, at least about 0.46 Å per cycle, at least about 0.48 Å per cycle, at least about 0.5 Å per cycle, or more.

In embodiments where multiple pulses of the nitrogen-containing precursor are flowed into the processing region for each pulse of oxygen-containing precursor, the amount of material etched per cycle of nitrogen-containing precursor may be any of the etch rates noted above. Atomic layer deposition may be performed to deposit any of the materials formed on the substrate, and may be used in general to produce a more conformal layer of material. Depending on the material being deposited and the process conditions, the growth rate may be about 0.35 Å per cycle of precursors. The present technology has been shown to be capable of performing an atomic layer etch of metal-containing materials that is characterized by an etch rate that is similar to or greater than the corresponding growth rates.

Other deposition methods may produce different etch rates as well. For example, physical vapor deposition may produce etch rates that are less than etch rates for materials formed with atomic layer deposition. Because physical vapor deposition often produces higher quality or denser films than atomic layer deposition, the amount of material removed per cycle of method 300 may be lower for such films. Accordingly, the number of cycles of method 300 performed may be greater depending on the quality of the film to be removed. The overall number of cycles of method 300 performed may be related to the depth of metal-containing material to be removed, but may be more than or about 5 cycles in embodiments. Additionally, aspects of method 300 may be repeated in at least about 10 cycles, at least about 20 cycles, at least about 50 cycles, at least about 75 cycles, at least about 100 cycles, at least about 150 cycles, at least about 200 cycles, at least about 250 cycles, at least about 300 cycles, at least about 350 cycles, at least about 400 cycles, at least about 450 cycles, at least about 500 cycles, at least about 550 cycles, at least about 600 cycles, at least about 650 cycles, at least about 700 cycles, at least about 750 cycles, at least about 800 cycles, at least about 850 cycles, at least about 900 cycles, at least about 950 cycles, at least about 1,000 cycles, or more depending on the amount of material to be removed. Both flowing and/or holding operations may be repeated per cycle, or certain operations may be repeated per cycle in embodiments. For example, for each cycle of flowing the oxygen-containing precursor, flowing the nitrogen-containing precursor may be repeated at least 10 times, and thus for 50 total cycles of flowing the oxygen-containing precursor, flowing the nitrogen-containing precursor may be repeated about 500 total cycles.

In some embodiments, the present technology may provide a halogen-free and plasma-free process for removing one or more metal-containing materials with an atomic layer etching that may be self-limiting. One, both, or all precursors used in method 300 may be halogen-free in embodiments, which may allow a more selective etch of metal-containing materials with respect to other exposed materials on the substrate surface. Additionally, method 300 may be performed in a plasma-free environment, and may involve no plasma precursors in embodiments. Radical precursors may interact with exposed materials in a physical manner that may sputter or otherwise etch materials on the surface irrespective of the film composition. By minimizing or eliminating plasma effluents within the processing region and chamber, a chemical-based etch may be performed that may allow selective etching of the metal-containing material over other materials on the substrate.

In embodiments plasma precursors may be utilized in one or more operations depending on the exposed materials on the substrate, and an amount of etching that may be acceptable on materials to be maintained during the etching process. Some materials may be formed or deposited to increased thickness in previous operations that may accommodate an amount of removal with respect to the metal-containing material intended to be etched. Plasma effluents may be produced externally to the processing chamber, or within the processing chamber. A remote plasma unit may be fluidly coupled with the processing chamber, and may provide radical effluents to the substrate. Within the processing chamber plasma may be formed at the substrate level, or may be produced in a region of the chamber physically separate from but fluidly coupled with the substrate processing region. By producing plasma remotely from the substrate, a sputtering component from plasma particles may be limited. For example, plasma may be produced in a capacitively-coupled, inductively-coupled, microwave, or other plasma formed upstream of the substrate processing region prior to flowing the plasma effluents into the substrate processing region.

One or more precursors may be excited via a plasma process, including carrier gases that may be flowed with the precursors. In some embodiments an oxygen-containing precursor may be flowed into a remote plasma region where a plasma may be formed to produce radical effluents. The plasma effluents may be provided to the substrate processing region, such as through a faceplate or showerhead as discussed previously, and may interact with the substrate including exposed regions of the metal-containing material. The plasma effluents may oxidize or assist in oxidizing the metal-containing material. The plasma may be formed from any oxygen-containing precursor, such as oxygen in embodiments, and may be used with or alternatively to water vapor or other oxygen-containing precursors. For example, the oxygen-containing plasma effluents may be used alone or may be used in conjunction with a water pulse as previously discussed. A water pulse may be provided to the substrate processing region and then oxygen-containing plasma effluents may be delivered to the processing region to further interact with the substrate surfaces.

As noted the plasma precursors may interact with any exposed materials on the surface of the substrate, and so in embodiments where additional material removal may be limited, the process may be performed plasma free. The plasma used in some embodiments may also be a low-power plasma, and may be below about 1000 W. Additionally, the plasma power applied to the oxygen-containing precursor may be below or about 900 W, below or about 800 W, below or about 700 W, below or about 600 W, below or about 500 W, below or about 400 W, below or about 300 W, below or about 200 W, below or about 100 W, or less in embodiments.

Turning to FIGS. 4A-4B are shown cross-sectional views of substrate materials on which selected operations are being performed according to embodiments of the present technology, which may include back-end-of-line hard mask removal. The substrates may include layered regions of oxide, nitride, polysilicon, copper, black diamond, low-k dielectric, or other materials as would be understood by the skilled artisan. The simplified schematic illustrated in FIG. 4A includes a substrate 405 having a metal-containing material 410 a formed on regions of the substrate 405. Although not illustrated, the substrate may include exposed regions of many different materials as discussed above along with exposed regions of hard mask material such as metal-containing material 410 a. The metal-containing material may be residual material for removal subsequent a patterning process, for example. The removal may be performed according to the present technology, which may allow etching of the metal-containing material without or with limited effect on other exposed materials.

The removal process may involve exposing metal-containing material 410 a to an oxygen-containing precursor, such as water vapor or some other oxygen-containing material. The oxygen-containing precursor may modify or oxidize the metal-containing material 410 a to a depth that may be up to or about 0.1 Å in embodiments, and may be greater than or about 0.12 Å, greater than or about 0.14 Å, greater than or about 0.16 Å, greater than or about 0.18 Å, greater than or about 0.2 Å, greater than or about 0.22 Å, greater than or about 0.24 Å, greater than or about 0.26 Å, greater than or about 0.28 Å, greater than or about 0.3 Å, greater than or about 0.32 Å, greater than or about 0.34 Å, greater than or about 0.36 Å, greater than or about 0.38 Å, greater than or about 0.4 Å, or greater, and may be any range between any two of these listed numbers or within a smaller range encompassed by any of these ranges.

To allow adequate time for interaction, the oxygen-containing precursor may be maintained within the substrate processing region for a period of time as discussed above. Remaining or unreacted oxygen-containing precursor may be purged from the chamber in embodiments. Subsequently, a nitrogen-containing precursor, such as an amine as previously discussed, may be delivered to the processing region, where it may interact or react with the modified or oxidized portion of the metal-containing material 410 a. This interaction may produce a volatile complex that desorbs from the surface of the substrate and metal-containing material at processing temperatures, and may be purged from the processing region of the chamber. As illustrated in FIG. 4B, metal-containing material 410 b has been reduced while substrate 405 has limited modification, which may be substantially or essentially no interaction. The process may be repeated for a number of cycles as previously discussed to remove additional metal-containing material, and may remove all metal-containing material in embodiments.

FIG. 5 shows a chart of various materials that may be exposed on a surface of a substrate on which a metal-containing material may be removed using operations of the previously discussed methods. In embodiments the metal-containing material may be titanium nitride, and may be or include other nitride or metal-containing materials. Additionally exposed materials may include silicon oxide, hafnium oxide, other metal oxides, black diamond or other low-k dielectrics, copper or other metals, nitride materials such as tantalum nitride, etc. As shown in the chart, methods according to the present technology may selectively etch titanium nitride with respect to these other materials. In embodiments, titanium nitride may be etched at a selectivity greater than or about 10:1 with respect to most other materials, and may be etched at a selectivity greater than or about 20:1, greater than or about 30:1, greater than or about 40:1, greater than or about 50:1, greater than or about 60:1, greater than or about 70:1, greater than or about 80:1, greater than or about 90:1, greater than or about 100:1, or greater, and in some embodiments, there was substantially or essentially no loss for other materials on the substrate, providing complete selectivity between titanium nitride and these other materials.

Tantalum nitride displayed an amount of etch loss with respect to titanium nitride over 500 cycles of atomic layer etching according to the present technology. While greater than 15 nm of titanium nitride was etched with the technology, tantalum nitride displayed less than 2 nanometers of removal. Depending on the number of cycles performed, titanium nitride may be etched respective to tantalum nitride with a selectivity greater than or about 5:1, greater than or about 6:1, greater than or about 7:1, greater than or about 8:1, greater than or about 9:1, greater than or about 10:1, greater than or about 12:1, greater than or about 15:1, or more. Additionally, tantalum nitride may be etched respective to the other listed materials at a selectivity of any of the numbers previously stated depending on the number of cycles performed, as the process of the present technology additionally etched tantalum nitride while substantially maintaining the other materials.

In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology.

Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a layer” includes a plurality of such layers, and reference to “the precursor” includes reference to one or more precursors and equivalents thereof known to those skilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups. 

The invention claimed is:
 1. A method of etching a semiconductor substrate, the method comprising: flowing an oxygen-containing precursor into a substrate processing region housing the semiconductor substrate, wherein the semiconductor substrate includes an exposed metal-containing material, wherein the oxygen-containing precursor comprises water, ozone, or radical oxygen; flowing a nitrogen-containing precursor into the substrate processing region; and removing an amount of the metal-containing material.
 2. The method of etching a semiconductor substrate of claim 1, wherein the oxygen-containing precursor is configured to react with the metal-containing material to produce a modified metal-containing material.
 3. The method of etching a semiconductor substrate of claim 2, wherein the nitrogen-containing precursor is configured to react with the modified metal-containing material to produce a volatile complex.
 4. The method of etching a semiconductor substrate of claim 1, wherein the nitrogen-containing precursor comprises an amine.
 5. The method of etching a semiconductor substrate of claim 4, wherein the amine comprises diethylamine, propylamine, or N-ethylmethylamine.
 6. The method of etching a semiconductor substrate of claim 1, wherein the oxygen-containing precursor and the nitrogen-containing precursor are flowed sequentially into the substrate processing region.
 7. The method of etching a semiconductor substrate of claim 6, further comprising holding for a first period of time subsequent flowing the oxygen-containing precursor and prior to flowing the nitrogen-containing precursor.
 8. The method of etching a semiconductor substrate of claim 7, wherein the first period of time is between about 5 seconds and about 30 seconds.
 9. The method of etching a semiconductor substrate of claim 6, further comprising holding for a second period of time subsequent flowing the nitrogen-containing precursor.
 10. The method of etching a semiconductor substrate of claim 9, wherein the second period of time is between about 10 seconds and about 60 seconds.
 11. The method of etching a semiconductor substrate of claim 1, wherein the oxygen-containing precursor comprises water or ozone and the nitrogen-containing precursor is halogen free, and wherein the method comprises a plasma-free process.
 12. The method of etching a semiconductor substrate of claim 1, wherein the method is performed at a temperature of between about 100° C. and about 225° C.
 13. The method of etching a semiconductor substrate of claim 1, wherein flowing the oxygen-containing precursor and flowing the nitrogen-containing precursor are repeated in at least one additional cycle.
 14. The method of etching a semiconductor substrate of claim 1, wherein the metal-containing material comprises titanium nitride.
 15. A method of etching a semiconductor substrate, the method comprising: forming plasma effluents of an oxygen-containing precursor in a remote plasma region of a semiconductor processing chamber; flowing the plasma effluents into a substrate processing region housing the semiconductor substrate, wherein the semiconductor substrate includes an exposed metal-containing material, wherein the substrate processing region is fluidly coupled with the remote plasma region, and wherein the oxygen-containing precursor is configured to react with the metal-containing material to produce a modified metal-containing material; holding for a first period of time greater than or about 1 second; flowing a nitrogen-containing precursor into the substrate processing region, wherein the nitrogen-containing precursor is configured to react with the modified metal-containing material to produce a volatile complex; holding for a second period of time greater than or about 1 second; and removing an amount of the metal-containing material.
 16. The method of etching a semiconductor substrate of claim 15, further comprising flowing additional nitrogen-containing precursor into the substrate processing region.
 17. The method of etching a semiconductor substrate of claim 15, wherein the method removes at least about 0.2 Å per cycle of flowing the plasma effluents and flowing the nitrogen-containing precursor into the substrate processing region.
 18. The method of etching a semiconductor substrate of claim 15, wherein the nitrogen-containing precursor is selected from the group of precursors consisting of a water-methylamine solution, a water-ethylamine solution, diethylamine, propylamine, dipropylamine, a water-diethylamine solution, and N-ethylmethylamine.
 19. The method of etching a semiconductor substrate of claim 15, wherein the plasma effluents are produced at a plasma power below or about 500 W.
 20. A method of etching a semiconductor substrate, the method comprising: flowing an oxygen-containing precursor into a substrate processing region housing the semiconductor substrate, wherein the semiconductor substrate includes an exposed metal-containing material; flowing a nitrogen-containing precursor into the substrate processing region; and removing an amount of the metal-containing material, wherein the oxygen-containing precursor and the nitrogen-containing precursor are halogen free, and wherein the method comprises a plasma-free process. 